Cardiac myosin binding protein C (cMyBP-C) is a regulatory protein of the cardiac sarcomere that contributes to contractile reserve. Mutations in cMyBP-C are a leading cause of hypertrophic cardiomyopathy (HCM), a disease that affects about 1 in 500 people worldwide. Truncation mutations in cMyBP-C cause HCM primarily through haploinsufficiency; however, the pathogenesis of disease-causing missense mutations is not well understood. The C-terminal domains are essential for incorporation into the sarcomere, while the N-terminal domains modulate contraction through phosphorylation-dependent inhibitory interactions. The role of the central domains in the physiologic function of cMyBP-C is unclear. The R495Q and R502W mutations in the C3 domain of cMyBP-C are among the most prevalent causes of HCM, however exactly how they affect function and contribute to the pathologic phenotype remains unknown. Studies suggest that mutations in this region may disrupt a putative protein binding domain. Given their location in the C3 domain we hypothesize that the R495Q and R502W mutations modulate contractility by modifying an interaction between domain C3 and an as-yet undefined ligand. In this pre-doctoral proposal, we will express mutant R495Q and R502W cMyBP-C in murine three-dimensional cardiac tissue constructs followed by assessment of contractility, calcium handling, calcium sensitivity and responsiveness to beta-adrenergic stimulation. To identify the mechanism linking these mutations to HCM, we will use contemporary proteomics approaches to define the function of the C3 domain and assess whether these mutations alter putative protein-protein interactions. Determining the function of the C3 domain will provide insight into the overall function of cMyBP-C, the pathogenesis of HCM, and may identify novel treatment strategies to prevent or modify disease progression. This pre-doctoral research proposal is part of a comprehensive training program which takes full advantage of the strong research environment at the University of Wisconsin-Madison to enhance the candidate's likely transition to a successful biomedical research scientist.